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Mobile ViewAIR CONDITIONING & HEAT PUMP SYSTEMS A/C - HEAT PUMP CONTROLS & SWITCHES A/C DATA TAGS A/C - HEAT PUMP CRITICAL DEFECTS A/C DIAGNOSTIC FAQs A/C REFRIGERANTS A/C TYPES, ENERGY SOURCE AGE of AIR CONDITIONERS & HEAT PUMPS AIR CONDITIONER BTU CHART AIR CONDITIONER COMPONENT PARTS AIR CONDITIONER TYPES, ENERGY SOURCES AIR CONDITIONER NOT WORKING AIR FILTERS for HVAC SYSTEMS Air Filter Accessibility Air Filter Bypass Leakage Air Filter Installation Procedure Build Large Air Filters Air Filter Location Dirty Air Filter Problems ENERGY SAVINGS by AIR FILTERS Air Filtering Strategies Missing or Leaky Air Filters AIR FILTERS, OPTIMUM INDOOR Air Filter Efficiency Optimum Air Filter Design / Location How to Cascade Air Filters CONTINUOUS BLOWER FAN OPERATION AIR FILTER EFFECTIVENESS MERV, HEPA Definitions MERV Air Filter Ratings How Air Filters Work Particle Sizes & IAQ Gasketed air filters Debris in Return Air Plenum Washable air filters AIR FILTERING STRATEGIES FIBERGLASS & AIR FILTERS Air Filters Shed Fibers? Fiberglass & Test Lab Accuracy Variations in Fiber Size SOURCES FOR AIR FILTERS OTHER AIR CLEANERS AIR HANDLER / BLOWER UNITS ADDING A/C: RETROFIT SIZING BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BLOWER LEAKS, RUST & MOLD COOLING / EVAPORATOR COIL DEFECTS DAMAGED COOLING COIL DIRTY A/C BLOWERS Leaks, Rodents In Air Handlers Mold Growth in Air Handlers DIRTY COOLING COIL DIRTY COIL CLEANING PROCEDURES FROST BUILD-UP on AIR CONDITIONER COILS ANIMAL ALLERGENS / PET DANDER ANIMAL ENTRY POINTS in buildings ANIMAL ODORS IN buildings APPLIANCE EFFICIENCY RATINGS ASBESTOS IDENTIFICATION IN buildings BACKUP HEAT for HEAT PUMPS BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BOOKSTORE - Air Conditioning "How To" Books CAPACITORS for HARD STARTING MOTORS CAPILLARY TUBES CHINESE DRYWALL HAZARDS CIRCUIT BREAKER SIZE for A/C or HEAT PUMP CLEANING & Legionella BACTERIA COMPRESSOR CONDENSER CONDENSATE HANDLING, A/C CONDENSATION or SWEATING PIPES, TANKS COOL OFF HEAT Thermostat Switch COOLING CAPACITY, RATED COOLING COIL or EVAPORATOR COIL COOLING LOAD REDUCTION by ROOF VENTS COMBUSTION GASES & PARTICLE HAZARDS CONDENSATE HANDLING, A/C CONDENSATION or SWEATING PIPES, TANKS DATA TAGS on AIR CONDITIONERS DEFINITION of Heating & Cooling Terms DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP DIAGNOSE & FIX HEATING PROBLEMS-BOILER DIAGNOSE & FIX HEATING PROBLEMS-FURNACE DUCT SYSTEM & DUCT DEFECTS DUCTS - Asbestos AIR FILTERS for HVAC SYSTEMS ALLOY SYSTEMS FLEXDUCT ASBESTOS HVAC DUCTS ASBESTOS PAPER on DUCTWORK ASBESTOS TRANSITE DUCTWORK BALANCING AIR DUCT FLOW DUCT & AIR HANDLER ODORS DUCT DAMAGE, MECHANICAL DUCT INSULATION - Asbestos Paper DUCT ROUTING & SUPPORT DUST CONTAMINATION FROM HVAC? FIBERGLASS DUCT, RIGID CONSTRUCTION FIBERGLASS HVAC DUCTS GOODMAN GRAY FLEXDUCT INCREASING RETURN AIR LEAKY DUCT CONNECTIONS LOCATION OF REGISTERS & DUCTS MOLD in AIR HANDLERS & DUCT WORK NOISES in DUCT SYSTEM ODORS in AIR HANDLERS & DUCT WORK OWENS CORNING FLEXDUCT OWL FLEXDUCT RETURN AIR REGISTERS & DUCTS SOUNDPROOFING for DUCTWORK SUPPLY DUCTS & REGISTERS TRANSITE PIPE AIR DUCTS UNDERSIZED RETURN DUCTS UNSAFE DUCT OPENINGS VIBRATION DAMPENERS WET CORRODED DUCT WORK DUCT INSULATION, Asbestos Paper DUCT INSULATION for SOUNDPROOFING DUCT SYSTEM NOISES DUCTS, Asbestos Transite Pipe DUST CONTAMINATION FROM HVAC? EDUCATION, HVAC SCHOOLS ELECTRIC MOTOR DIAGNOSTIC GUIDE ELECTRIC MOTOR OVERLOAD RESET SWITCH ELECTRICAL POWER SWITCH FOR HEAT ENERGY SAVINGS in buildings EVAPORATIVE COOLING SYSTEMS EVAPORATOR COIL or COOLING COIL EXPANSION VALVES, REFRIGERANT FAN, AIR HANDLER BLOWER UNIT FAN AUTO ON Thermostat Switch FAN, COMPRESSOR/CONDENSER UNIT FAN CONVECTOR HEATERS - HYDRONIC COILS FAN LIMIT SWITCH FAN NOISES FURNACES WARM AIR HEATING SYSTEMS GASES, EXPOSURE, TESTING Carbon Dioxide - CO2 Carbon Monoxide - CO METHANE GAS SOURCES GAS MEASUREMENT TOOLS GAUGE, REFRIGERATION PRESSURE TEST HEAT LOSS (or GAIN) in buildings HEAT PUMPS HUMIDITY LEVEL TARGET INDOOR AIR QUALITY IMPROVEMENT GUIDE INSPECTION LIMITATIONS LEED GREEN BUILDING CERTIFICATION LOST COOLING CAPACITY MANUALS & PARTS GUIDES - HVAC MOTOR OVERLOAD RESET SWITCH NOISY AIR CONDITIONER / HEAT PUMP NOISE / SOUND DIAGNOSIS & CURE Air Leak Noises AIR CONDITIONING & HEAT PUMP NOISES OPERATING COST OPERATING DEFECTS OPERATING TEMPERATURES PORTABLE ROOM AIR CONDITIONERS PRESSURE READINGS, REFRIGERANT REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS REPAIR & DIAGNOSTIC FAQs for A/C REFRIGERANTS RETROFIT SIZING for A/C or HEAT PUMPS SEER RATINGS & OTHER DEFINITIONS SOLAR ENERGY SYSTEMS SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS SWAMP COOLERS SYSTEM OPERATION THERMOSTATS, HEATING / COOLING THERMOSTATIC EXPANSION VALVES WATER COOLED AIR CONDITIONERS More Information |
This article explains how and why to set your air conditioning or heating system blower fan to continuous operation in order to improve indoor air quality by increased and continuous indoor air filtration. (Naturally if there is an IAQ problem source in the building it is essential to also find and correct that condition. InspectAPedia offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/Contact.htm.This website answers almost any question you might ask about air filters for heating or air conditioning systems. Readers should also see our INDOOR AIR QUALITY IMPROVEMENT GUIDE article series. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Why Run an Air Conditioner or Heating Blower Fan Continuously?For maximum IAQ improvement in buildings: for the new blower installation we selected a fan unit which had both the capability of delivering adequate CFM of air flow and a blower fan motor duty cycle which permits continuous operation if we wish to run the system that way. Running the blower continuously at low speed resulted in continual air scrubbing in the building. When the heating or cooling needs of the building require, the fan shifts automatically to high speed. Here are the details: Here are some possible advantages of continuous blower fan operation
Here are some disadvantages of continuous air conditioner or heating system blower fan operation
How to Put the Air Conditioner or Heat Pump Blower Fan into Continuous-On Operation
Air Filtration SuggestionsSee these articles about how to use air filters, where to buy them, and how to turn on and off HVAC blower fans
Questions & Answers regarding this articleQuestions & Answers about whether or not to run the heating or air conditioning blower fan continuously Question: what is the relationship between continuous blower fan operation and indoor humidity where central air is installed? Can condensate in the air handler raise indoor humidity?Edgardo: A disadvantage I found running the AC fan continuously in my residence, was a noticeable increase in the humidity in the house. The fan would blow across the wet coils and drain pan while the compressor wasn't running and put the water it had removed from the air during the prior cooling cycle back into the living space. So I stopped doing that. - Edgardo Reply: from DF Edgardo, thanks for the comment, it's an opportunity to clear up some confusion. You should not see standing water there ever. If you do, the drip tray is not draining and the tray or drain system need to be cleared and repaired. Details about condensate handling are in the article titled CONDENSATE HANDLING, A/C and details about target levels for indoor humidity are at HUMIDITY LEVEL TARGET. Edgardo: Hi Dan The pan drains fine, and the backup secondary pan is dry. I am not seeing any unusual amount of water. The problem I mentioned is caused simply by evaporation back into the living space of the residual condensation left on the coils and in the pan when the compressor shuts off. The parts can't be instantly dry when the compressor shuts off. Anyway I do run the fan more continuously in the winter, as between cycles the air will settle in the house and can be close to 50° at the floor when it's 75° 5 feet off the floor. Keeping the fan on keeps the air mixed up and I can run the heat a degree or two lower. Dan: Edgardo I'm surprised that the volume of water left on the cooling coil after the A/C system shuts off would provide a measurable quantity of total humidity in the living space. Consider the total volume of water that's resting on the coils (as you explain the drain pan is dry) - it has to be less than a quart. Evaporate a quart of water into the cubic feet of air in even a small home - it just would not be likely to explain an indoor humidity problem. Edgardo: I mentioned before that the main pan drains fine, but it will still be wet until the residual evaporates, and the secondary pan is dry which is there in case the primary pan drain gets clogged. There should never be water in that secondary catch pan otherwise the main drain is clogged. Anyway, all that is normal. I have access to the condensate drain pipe, and yesterday afternoon I put it into a gallon jug and captured almost a half-gallon of condensate water in 1 hour. Relative humidity in the house right now is 42%. Temperature is 78°. I have a 1953-built frame house that I think cost about $8,000 new when it was built. Needless to say it has lousy insulation and leaks air everywhere, and moisture up from the crawl space. So I think the AC does well all things considered. Oversized system? Don't think so. It can just keep up with the heat load, and cycle off once in a while when it's 100°+ outside. We have some pretty extreme summer weather and humidity conditions in Texas and the system handles it pretty well with reasonably low electricity usage. Dan: Edgardo I agree that if your RH is down to 42% that's a suggestion that the A/C is both cooling and dehumidifying and is not oversized. Perhaps taking some RH measurements at regular intervals and when the system is cycling on and off will give a more clear picture of the indoor RH. It just doesn't seem likely to me that the volume of moisture residual in a wet but otherwise drained condensate pan would explain a measurable variation in indoor RH in the rest of the building. That volume of water evaporated into the volume of air in a building could not explain high indoor RH. It may be more likely that if the home is poorly insulated and more, drafty, indoor Rh climbs along with temperature between cooling cycles. Also if the RH was coming from the ductwork as a prime source when the system is off, you'd find higher RH at the duct openings as well as evidence of airflow out of the ducts when the cooling system was off. But be sure to measure RH at both the return and supply sides and registers so we're not confused by cycling higher RH house air with moisture coming from other sources or outdoors. Some measurements ought to clear that up. Please also be sure to take a look at DEHUMIDIFICATION PROBLEMS where we describe some sources of and cures for high indoor humidity in buildings. Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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